The Visit of the Royal Physician, Per Olov Enquist, trans. Tiina Nunnally

Per Olov Enquist's gripping tragedy of passion and revolution has won the'Independent' Foreign Fiction Prize. Boyd Tonkin hails the Swedish conqueror

The Swedish novelist, playwright and screenwriter Per Olov Enquist has won the Independent Foreign Fiction Prize for The Visit of the Royal Physician. A prolific, innovative and often controversial figure in Swedish and Scandinavian culture since the Sixties, Enquist shares the £10,000 award with his translator, Tiina Nunnally. Already a success in 20 countries, Enquist's historical drama has taken the best foreign novel award in France and Sweden's August Prize. It has also just reached the shortlist of this year's International IMPAC Award.

This is the 68-year-old author's first major British honour. Yet many English-language critics have already agreed with the assessment of this year's Independent prize panel (Ahdah Soueif, Jack Mapanje, Professor Susan Bassnett, Amanda Hopkinson and Boyd Tonkin). Caroline Moore of the Sunday Telegraph described The Visit of the Royal Physician as "hovering brilliantly and most strangely between bald historical fact and poetic fiction". In the Daily Telegraph, Kathryn Hughes called the novel's feeling "dream-like, the style spare, the effect utterly beguiling". For the Los Angeles Times, Jonathan Levi applauded "an extraordinarily elegant and gorgeous novel". In World Literature Today, Anna Patterson simply paid tribute to "an almost perfect historical novel".

Born in rural northern Sweden in 1934, Enquist has published fiction for 40 years (since The Crystal Eye in 1961). He combines a modernist's fascination with experiment and an investigative journalist's nose for the historical incident – recent or remote – that can shed light on an entire era and society. Sometimes, this blend of documentary density and taut, elliptical storytelling brings to mind a writer such as E L Doctorow. But Enquist's image-rich and cliché-free historical narration, probing at the limits of our knowledge, also provokes a more unlikely comparison. He can sound like the Beryl Bainbridge of Every Man for Himself or Master Georgie.

Many of Enquist's best-known works of fiction stem, like The Visit of the Royal Physician, from thoroughly researched actual events. They include The Legionnaires (1968), based on the German troops who fled to Sweden at the end of the war, and The March of the Musicians (1978), set among exploited sawmill workers. Enquist has also worked in the Swedish and Danish theatre for 30 years and, as a screenwriter, has helped create films that include Bille August's Pelle the Conqueror.

The Visit of the Royal Physician relates the true tale of an abortive Danish revolution in the 1770s, and the backlash that crushed it. Its flinty, lyrical and fast-moving style has been brought immaculately into English by Tiina Nunnally.

Caroline Mathilde, youngest sister of George III of England, is married off as "breeding stock" to the disturbed teenage king of Denmark, Christian VII. In this feudal backwater, the reactionary nobles rule; the inbred puppet-kings perform; the people mutely suffer. Then the strong-minded English bride meets Struensee – a dashing court doctor from Germany, imbued with all the idealism of the Enlightenment.

The pair form an alliance against the religious zealot, Count Guldberg. Their friendship deepens into an passionate affair. Struensee assumes the regency of Denmark. His whirlwind revolution-from-above abolishes torture, unyokes the serfs, shakes the nobility, frees the press, and speeds the country from the most archaic to most advanced of European states.

Inevitably, it all ends in blood and terror. Struensee and Caroline Mathilde have no power-base beyond the wretched king. Guldberg and the old guard regroup, and stage a counter-coup. Struensee, who banished torture, becomes the victim of its comeback. He dies on the scaffold; and his lover is bundled into exile.

There's a happy coda. The couple have had a daughter, Louisa Augusta. A generation later, with Struensee's legacy once more honoured, she re-joins the bloodlines of European nobility. "Today, there is hardly any European royal house" that cannot trace its lineage back to Struensee and Caroline Mathilde. I reckon that – thanks to the Danish forebears of Philip, Prince of Greece – that roll of heirs now includes the House of Windsor.

It would be child's play to underscore the novel's modern echoes. The teenage English princess who takes a doctor lover and, iron-willed, schemes her way into authority; the clique of utopians who believe that freedom must be imposed on traditional folk; the clash of values between secular, liberal Struensee and the rigid fundamentalism of Guldberg ... All of that matters to the novel, but what makes it a marvel is the ferocity and intensity of its swift human drama.

Whatever you may find hackneyed about period fiction, rest assured that Enquist knows just how to avoid it. He shuns hindsight and lets the past safeguard its mysteries. His people never act like periwigged marionettes on an over-dressed stage (although he cleverly explores poor King Christian's obsession with the theatre). Enquist's figures love and hate and plot with an incandescent energy that wipes out emotional distances.

The novel's final act – the revolution's defeat and Struensee's humiliation – builds into a bleakly touching vista of personal and political collapse. "How could someone conquer the world if he was only good, and lacked the courage to be evil?" asks the terrified, still-naive doctor. "How was it then possible to put a lever under the house of the world?" Reformers and idealists of every stripe are still looking for that lever.

'The Visit of the Royal Physician' is in Vintage paperback from 1 May